Field-effect passivation of metal/n-GaAs Schottky junction solar cells using atomic layer deposited Al2O3/ZnO ultrathin films

In this paper, a novel field-effect passivation technique is used to improve the photovoltaic properties of metal/n-GaAs Schottky junction solar cells. In this technique, a relatively large density of positive or negative fixed charges existing at the top surface of the dielectric thin films is used to create an electric field gradient to prevent the photogenerated charge carriers from recombining. Atomic layer deposition is used to grow high-quality Al2O3 and ZnO ultrathin films that are used as passivating materials. Electrical measurements demonstrate an improvement in both diodelike and photovoltaic properties of Schottky solar cells in the proposed stacked Al2O3/ZnO passivation structure compared to the single Al2O3 layer. This can be attributed to both higher equivalent capacitance/permittivity of the stacked passivation layer and increased density of negative fixed charges at the interface of the passivation layer and the semiconductor.